NEW RIVER LOCHY–MOWI STUDY TO MONITOR SALMON-ESCAPE IMPACTS

New River Lochy–Mowi study to monitor salmon-escape impacts. The River Lochy Association and Mowi Scotland have agreed a long term and wide-ranging scientific study to examine the potential impacts of the salmon escape from Mowi’s Gorsten farm in October. The study, funded by Mowi, which will also utilise the genetic expertise of the Institute for Biodiversity and Freshwater Conservation at UHI Inverness, will allow Mowi Scotland and the River Lochy Association to monitor and mitigate any adverse impacts on the salmonid biology within the catchment area.

Following a salmon escape from Mowi’s Gorsten salmon farm in Upper Loch Linnhe on 5^th October 2025 as a result of the extreme weather conditions experienced during Storm Amy, an estimated 75,000 salmon with an average weight of 860g escaped into the wild. The fish were sexually immature and were from RAS (Recirculating Aquaculture System) origin with a very low level of survival in the wild expected. The immediate actions taken by Mowi, in consultation and coordination with the River Lochy Association, were as follows:

• Immediate recapture of fish that entered local and more distant rivers. Due to the timing of the escape so close to the salmon and trout spawning season, and the height of the rivers at the time, it was decided not to use nets but to rod catch as many fish as possible.
• Over 100 anglers were deployed throughout the region and beyond. All captures were reported on the Fisheries Management Scotland escapes reporting app. As at the time of publishing, 440 captures (all immature and weighing 0.5 to 2.5kg) have been reported, with the vast majority in the lower reaches of the Rivers Lochy and Leven.

Mowi and the River Lochy Association have now agreed the scope of a long-term study which will include the following:

• Scale samples will be taken from the majority of rod-caught adult returning salmon in both the Lochy and Leven rivers in 2026 and 2027. These samples will be genetically screened against the farm stock to ascertain the level (if any) of farmed fish from this escape in the returning adult fish from the ocean.
• In 2026 local teams of fisheries biologists will undertake timed electro-fishing surveys on all major salmon catchments in the Upper Linnhe region and take samples of fry for genetic screening. This will form the baseline ‘pre-incident’ survey. 58 known fry sampling sites will be used with a wide geographic spread of sites in each catchment. A minimum of 20 and a maximum of 30 fry will be sampled at each site using non-lethal caudal fin clips taken from anaesthetised fish.
• In 2027 and 2028 the above fry sampling will be repeated, and these years will be used to detect the genetic impact (if any) in the wild population from this escape event.

Commenting on the plan, Jon Gibb, Manager of the River Lochy Association and Director of the Lochaber District Salmon Fishery Board, said:

“Obviously an escape of farmed salmon into the wild is something that nobody wants to see. But I am confident that between Mowi and the River Lochy Association, the local wild fishery management body, that we have designed a comprehensive three-year genetic monitoring plan that will definitively identify whether there will be any impact whatsoever from this unfortunate incident on the local wild salmon population.”

Stephen MacIntyre, Head of Environment at Mowi Scotland, added:

“While we are disappointed this incident occurred, we acknowledge our responsibility to monitor and assess the potential for any adverse impacts on local wild salmon populations. Using this scientific approach, the monitoring study will determine whether there is evidence of any changes in the genetic composition of wild salmon arising from the escape incident. We look forward to supporting the delivery of the study with the River Lochy Association over the next three years.”

Image: River Lochy Association and Mowi Scotland